KVM: MMU: fix wrong not write protected sp report

The audit code reports some sp not write protected in current code, it's just the
bug in audit_write_protection(), since:

- the invalid sp not need write protected
- using uninitialize local variable('gfn')
- call kvm_mmu_audit() out of mmu_lock's protection
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

arch/x86/kvm/mmu.c

@@ -3708,16 +3708,17 @@ static void audit_write_protection(struct kvm_vcpu *vcpu)
 	struct kvm_memory_slot *slot;
 	unsigned long *rmapp;
 	u64 *spte;
-	gfn_t gfn;
 
 	list_for_each_entry(sp, &vcpu->kvm->arch.active_mmu_pages, link) {
 		if (sp->role.direct)
 			continue;
 		if (sp->unsync)
 			continue;
+		if (sp->role.invalid)
+			continue;
 
 		slot = gfn_to_memslot(vcpu->kvm, sp->gfn);
-		rmapp = &slot->rmap[gfn - slot->base_gfn];
+		rmapp = &slot->rmap[sp->gfn - slot->base_gfn];
 
 		spte = rmap_next(vcpu->kvm, rmapp, NULL);
 		while (spte) {

arch/x86/kvm/paging_tmpl.h

@@ -504,7 +504,6 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
 	unsigned long mmu_seq;
 
 	pgprintk("%s: addr %lx err %x\n", __func__, addr, error_code);
-	kvm_mmu_audit(vcpu, "pre page fault");
 
 	r = mmu_topup_memory_caches(vcpu);
 	if (r)
@@ -542,6 +541,8 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
 	spin_lock(&vcpu->kvm->mmu_lock);
 	if (mmu_notifier_retry(vcpu, mmu_seq))
 		goto out_unlock;
+
+	kvm_mmu_audit(vcpu, "pre page fault");
 	kvm_mmu_free_some_pages(vcpu);
 	sptep = FNAME(fetch)(vcpu, addr, &walker, user_fault, write_fault,
 			     level, &write_pt, pfn);